Colloidal Oxide Nanoparticle Inks for Micrometer-Resolution Additive Manufacturing of Three-Dimensional Gas Sensors

Micrometer-resolution 3D printing of functional oxides is of growing importance for the fabrication of micro-electromechanical systems (MEMS) with customized 3D geometries. Comparing to conventional microfabrication methods, additive manufacturing presents new...

Phase Change Temperature Sensor for High Radiation Environment

Performance of any sensor in a nuclear reactor involves reliable operation under a harsh environment (i.e., high temperature, neutron irradiation, and a high dose of ionizing radiation). In this environment, accurate and continuous monitoring of temperature is critical for the reactor's stability and proper functionality. Furthermore, during the development and testing stages of new materials and structural components for these systems, it is imperative to collect in-situ measurement data about the exact test conditions for real-time analysis of their performance. To meet the compelling need of such sensing devices, we propose radiation-hard temperature sensors based on the phase change phenomenon of chalcogenide glasses. The primary goal is to resolve the monitoring of the cladding temperature of light water and metallic or ceramic sodium-cooled fast reactors within a temperature range of 400°C to 600°C. This work is focused on studies of Ge-Se(S) chalcogenide glasses that have crystallization temperatures in this range. Each chalcogenide glass transforms and becomes crystalline at a specific heating rate at a definite temperature. As a result of this, both the electrical resistance and optical properties of the materials change. As this is the first time such devices have been fabricated, this work submits new data regarding materials research, various device structures, fabrication, performance, and testing under irradiation. The application of these materials in devices usually involves the formation of a thin film that works as an active layer. Traditionally, thin films are prepared by thermal evaporation, sputtering or chemical vapor deposition and they require high vacuum machinery and patterning applying photolithography. To avoid using such heavy machinery and costly fabrication processes, we investigate the formulation of nanoparticle inks of chalcogenide glasses, the formation of printed thin films using the inks, low-cost sintering and demonstrate their application in electronic and photonic sensors utilizing their phase transition effects. The printed chalcogenide glass films showed similar structural, electronic and optical properties as the thermally evaporated films. The newly developed process steps reported in this work describe chalcogenide glasses nanoparticle inks formulation, their application by inkjet printing and dip-coating methods and sintering to fabricate phase change temperature sensors. To interpret and predict the printed films' performance, Raman spectroscopy, X-ray Diffraction Spectroscopy, Energy Dispersion Spectroscopy, Atom Force Microscopy, temperature dependent Ellipsometry, and other methods are used. An essential part of materials' behavior is related to the materials' and devices' response to ion beam irradiation. Both experimental data and simulation are analyzed to study the effect of irradiation. Based on the different working principles, electrical, optical and plasmonic temperature sensors are investigated. An array of optical fiber devices fabricated with different chalcogenide glasses is shown to perform a real-time temperature reading. This work could be used as a paradigm for sensor fabrication and testing for high radiation environments and nanoparticle inks of chalcogenide glasses formulation and their application by inkjet printing and dip-coating. The most novel outcome of this work adds chalcogenide glasses to the list of inkjet printable materials, thus opening up an opportunity to achieve arbitrary structures for optical and electronic applications without photolithography.

Optimization of the conductivity of microwave components printed by inkjet and aerosol jet on polymeric substrates by IPL and laser sintering

In this work, microwave planar resonators are printed with silver nanoparticle inks using two printing technologies, inkjet printing and aerosol jet printing, on polyimide substrates. The microwave resonators used in this paper operate in the frequency band 5–21 GHz. The printing parameters, such as the number of printed layers of silver nanoparticle inks, drop spacing, and sintering time, were optimized to ensure repeatable and conductive test patterns. To improve the electrical conductivity of silver deposits, which are first dried using a hot plate or an oven, two complementary sintering methods are used: intense pulsed light (IPL) and laser sintering. This paper presents the results of different strategies for increasing the final quality factor of printed planar resonators and the trade-offs (sintering time versus final conductivity/unloaded Q) that can be reached. Improvement of the resonator unloaded quality factor (up to +55%) and of the equivalent electrical conductivity (up to 14.94 S/μm) at 14 GHz have been obtained thanks to these nonconventional sintering techniques. The total sintering durations of different combinations of sintering techniques (hot plate, oven, IPL, and laser) range from 960 to 90 min with a final conductivity from 14.94 to 7.1 S/μm at 14 GHz, respectively.